Nonwoven fabrics and fabric laminates are widely used in a variety of applications, for example, as components of absorbent products such as disposable diapers, adult incontinence pads, and sanitary napkins; in medical applications such as surgical gowns, surgical drapes, sterilization wraps, and surgical face masks; and in other numerous applications such as disposable wipes, industrial garments, house wrap, carpets and filtration media.
By combining two or more nonwoven fabrics of different types, nonwoven fabric laminates have been developed for a variety of specific end use applications. For example, nonwoven fabric laminates have been developed to serve as a barrier to penetration by air borne contaminants, such as microorganisms. Barrier fabric laminates of this type typically include one or more microfibrous polymer layers, such as meltblown webs, combined with one or more layers of another type of nonwoven fabric.
For example, filtration face masks, well known in the medical and respiratory art, typically include as a component thereof a microfibrous barrier layer. Such face masks can be worn over the breathing passages of a person and typically serve at least one of two purposes: (1) to prevent impurities or contaminants from entering the wearer's breathing tract; and (2) to protect others from being exposed to bacteria and other contaminants exhaled by the wearer. In the first situation, the mask could be worn in an environment were the air contains particulates harmful to the wearer. In the second situation, the mask could be worn in an operating room to protect a patient from infection.
Meltblown nonwoven fabrics can display excellent liquid, gas and particulate filtration properties, and accordingly, have been included in fibrous filtration face masks as barrier layers. Advantageously, the meltblown web provides good barrier properties when incorporated in the mask without adversely impacting the comfort of the wearer of the mask, i.e., the breathability of the mask, as measured by the drop in pressure across the fabric (.DELTA.P). Typically, the meltblown component includes microfibers having an average diameter ranging from about 1.8 to 3 microns, and higher, and has a basis weight ranging from about 20 to 40 grams per square meter. In addition, typically, meltblown webs used in face mask applications exhibit a drop in pressure across the fabric of about 2.0 to 3.0 millimeters of water in the meltblown web. Industry standards typically require a pressure drop of 1.5 to 2.0 in the filtration media, and 2.0 to 4.0 in the finished mask. A variety of face mask constructions are described in U.S. Pat. Nos. 4,920,960, 4,969,457, and 5,150,703, all to Hubbard et al.; U.S. Pat. No. 5,322,061 to Brunson; U.S. Pat. No. 4,807,619 to Dyrud et al.; U.S. Pat. No. 5,307,796 to Kronzer et al; U.S. Pat. No. 4,419,993 to Petersen; U.S. Pat. No. 4,662,005 to Grier-Idris; and U.S. Pat. No. 4,536,440 to Berg.
Despite these and other filtration media and face masks incorporating the same which are currently available, there exists a need to improve important filtration parameters, such as filtration efficiency and wearer comfort and breathability. In addition, it would be advantageous to provide filtration media having a light basis weight, which could also increase wearer comfort. However, increasing filtration efficiency can impair comfort and breathability.